Lipsticks are primarily made of lipophilic or hydrophobic materials. Lipsticks designed for providing a moisturizing benefit to the lips further contain water, polar solvents, or other moisturizing components which are more or less hydrophilic. The use of association structures have been suggested to bind such moisturizing components in the lipophilic matrix of the lipstick. While such lipstick compositions provide a favorable moisturizing benefit to the lips, they were not completely satisfactory in terms of physical stability, color stability, and sweat resistance.
Physical stability relates to the stability of the stick during storage and upon use. For example, a stable stick does not deform during storage at ambient temperature, and does not bend or break upon normal condition use. Color stability relates to the stability of color during storage and after application on the lip. It has been known that lipsticks containing a high amount of moisturizing components have the tendency to change color over time after application on the lip. Sweating is a phenomena seen on the surface of sticks, and is believed to be due to oils and/or solvents separating and leaking out of the lipophilic matrix of the stick. Sweating provides a negative appearance to the user.
Stability is also an important requirement for other lipophilic or anhydrous compositions such as liquid and powder foundations. For foundations, stability relates to color, viscosity, and phase condition.
Anhydrous cosmetic foundations containing alkyl dimethicone copolyols and polyols are disclosed, for example, in PCT publications WO 01/12137, WO 01/12138, WO 01/12139, and WO 01/12152. While such compositions are believed to provide physical stability, further improvement is desired, particularly for applying to lipophilic lipstick compositions.
Based on the foregoing, there is a need for a personal care composition which has improved stability over a wide range of product forms, and which can be made using conventional equipment for making personal care compositions. There is also a need for an anhydrous composition which as improved physical stability, improved color stability, and improved sweat resistance, while also providing moisturizing benefit to the lips.